`gb_mod` is broken

[LiterallyVoid]

gb_remainder uses round. this is bad, because it means gb_remainder(1.5, 2.0) = -0.5, and gb_mod(2.5, 2.0) = 2.5. this is contrary to how the C standard library modf / remainder functions work.

edit: it looks like gb_remainder is correct; but gb_mod is wrong.